Switch Traffic Redirection During IST Synchronization

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Solution Overview

Problem

Conventional Multi Chassis Switch Cluster technologies experience traffic loss during the synchronization process when a switch is brought up, as it does not have forwarding tables to handle incoming traffic until synchronization is complete, leading to potential seconds of lost traffic due to premature enabling of core network links.

Innovation Solution

Implementing a method that discovers paths within a virtual IST configuration, starts an IST synchronization process, installs redirection rules for data traffic, and removes them once synchronization is complete, allowing traffic redirection without requiring dedicated intra-cluster links.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If core network links are enabled when a switch comes up in Virtual IST configuration, then network robustness is improved by keeping the switch cluster up, but traffic loss increases because other switches send traffic to the new switch before it is ready to handle such traffic

Engineering Contradiction:

Improvenetwork robustnessVSAvoidtraffic loss

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent applies preliminary action by enabling core network links and starting routing protocols before the IST synchronization process completes, allowing the switch to be part of the network earlier. This resolves the contradiction by proactively establishing network connectivity while managing traffic flow through controlled redirection mechanisms.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary mechanism in the form of traffic redirection rules that intercept and redirect traffic intended for the new switch to alternative paths or existing cluster members during the synchronization period. This mediator prevents traffic loss by ensuring traffic is handled by ready switches while the new switch completes synchronization.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of substance

If a switch completes IST synchronization before enabling other links, then traffic loss is reduced during the synchronization process, but network robustness decreases because the switch cannot participate in network traffic handling during this period

Engineering Contradiction:

Improvetraffic lossVSAvoidnetwork robustness

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The patent performs preliminary actions by enabling core network links and participating in routing protocols before IST synchronization completes. This allows the switch to be network-active while managing incoming traffic through redirection, thus maintaining network robustness without causing traffic loss.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamic traffic redirection rules that adapt during the switch startup process. The redirection rules are installed temporarily during synchronization and removed afterward, allowing the system to dynamically adjust traffic flow based on the switch's readiness state, thereby maintaining both robustness and minimizing traffic loss.

Inventive Principle:

Principle #15Dynamics

3Reliability

If dedicated IST links are used for cluster switches, then control communication is reliable during switch startup, but device complexity and infrastructure requirements increase

Engineering Contradiction:

Improvecontrol communication reliabilityVSAvoidinfrastructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies universality by using existing core network links for multiple purposes: both for carrying data traffic and for IST control communication. This eliminates the need for dedicated IST links, reducing infrastructure complexity while maintaining control communication reliability through the multi-functional use of network resources.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the control communication function with data traffic paths by using the same core network links for both purposes. Instead of separate dedicated IST links, the control channel operates over shared network infrastructure, simplifying the overall system architecture while ensuring reliable control communication during switch startup.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9806998B2Method of reducing traffic loss when bringing up a switch within a multi chassis switch cluster without using dedicated intra cluster links

Publication Date: 2017.10.31 EXTREME NETWORKS INC

AI summary

A method, apparatus and computer readable medium for reducing traffic loss when bringing up a switch within a multi chassis switch cluster without using dedicated intra cluster links is presented. A first network device in a cluster discovers at least one path to a second network device in the cluster, wherein the cluster utilizes at least one virtual IST between the first network device and the second network device. The first network device starts an Inter Switch Trunk (IST) synchronization process with the second network device. The first network device installs redirection rules, wherein the redirection rules are used for datapath traffic and are not used for control channel traffic. The first network device determines that the IST synchronization process between the first network device and the second network device has completed, and removes the redirection rules.